Molded product



V Patented Jiine IS, 1940 10s. COMPOSITIONS, Y

COATING R PLASTIC.

Cross Referenc Examiner 2,204,913

MOLDED PRODUCT Allan B. Ruddle, San Francisco, Calif.

No Drawing. Application September 25, 1937, Serial No. 165,765

6 Claims. (01. 22-188) This invention relates to molded products, andparticularly to a composition for molding which has as its principalingredient sand or other similar granular or powdery substance.

The invention is adapted to the manufacture of various types of productswhich may be molded from sand to produce articles that are highlyresistant to either heat or moisture. For example, fire bricks,ornamental pottery, ornamental build- 10 ing stones and the like may bemade by the process of this invention.

One very extensive use of a molded sand product is the manufacture ofcores for metal casting purposes, and as the present invention isparticularly well adapted to this use, the following description of theinvention will be more or less confined to this particular application.The manner in which the invention may be applied to other than thisspecific use will however be apparent.

In present foundry practice, hollow castings are made by pouring metalinto a sand mold in which a sand core is supported to occupy theposition corresponding to the hollow portion of the completed casting.The core is usually constructed of ordinary molding sand, withingredients added to facilitate molding the sand to a definite shape andpermit baking the core to render it sufficiently hard and firm to standup under the 30 pouring of molten metal, yet friable enough to bereadily broken out of the completed casting.

The principal ingredient used for this purpose is vegetable oil, towhich is added other materials to make what is known to the trade ascore oil."

There are many varieties of core oils on the market for this purpose,all of which are supple mented in foundry practice by various specialmolding sands, powders, flours and the like, in an attempt to produce asatisfactory core. The

vegetable oils used, as well as many of the other ingredients, arecostly, and the results produced are neither uniform nor dependable.

It is the object of the present invention to provide a molded productsuch as may be used for a core and which is made entirely of inexpensiveingredients and that will produce a uniform, firm core; and to provide acore material that may be satisfactorily baked or cured withconsiderably less heat and in less time than is possible with materialsknown at the present time.

A further object of the invention is the provision of a molded productconsisting principally of sand and a siliceous binder which will behighly resistant to destruction by either heat or moisture.

65 Thus cores made in accordance with my invention are suificientlyresistant to moisture that they do not disintegrate in a moistatmosphere, and sufliciently resistant to heat so that they do not fallapart upon casting the molten metals.

As is well known, cores made with sodium silicate 5 alone are subject toboth these faults, and, as

a matter of fact, sodium silicate alone cannot be used as a binder forcores for these reasons. The diiiiculties' encountered with hydroscopiccores are described in the Hanley patent, U. S. No. 1,673,356. My cores,however, are not so hard that they will cause cracked castings. On thecontrary, extensive experiments in foundry work have shown that fewerfailures are obtained with my binder than with any other binder known to5 I have discovered that a satisfactory molded core may be made bymixing with common molding sand an alkali metal silicate, an alkalimetal fiuosilicate. and either an acid or an alum. It 0 is preferredthat the materials used for t s purpose be such as are available atrelatively low cost. Sodium silicate and sodium fiuosilicate meet thisrequirement and are typical of the alkali metal silicates andfiuosilicates that may 3 be used. Aluminum sulphate is an example of aninexpensive alum-like substance that is suitable for the purpose of thepresent invention. In making cores, I first prepare a solution in theproportions of about Water gallons 2 Aluminum sulphate ounces 1-10Alkali fluosilicate do 1-10 Alkali metal silicate gallons 1-10 I u Thesolution made within the limits of the above formula should be a clearliquid of approximately 30 to 32 Baum. One part by volume of thissolution is-then mixed with from 5 to 60 parts of common molding sand,depending upon the in use for which the product is being made. A core'material made in this manner is readily molded matter of fact,unnecessary to bake the product made in accordance with my invention, asexposure to the atmosphere at normal temperatures will, in a few hourstime, produce the desired effect. Baking, of course, hastens the curingof the cores.

dium tctraborate) may be added in quantities a .2 one ounce to onegallon of the above solution to render the resulting productsufficiently hard to give unusually good results in casting metalshaving very high fusing temperatures.

The customary reenforcing of iron wire or the like may be used in coresmade in accordance with my invention, but as my cores are firmer andless friable than ordinary cores, reenforcing may be eliminated in manyinstances where it would otherwise be necessary.

I have also discovered that mineral oils, which are ordinarilyunsatisfactory in the manufacture of cores because of the fact that theydo not cure or dry, are usable with the solution set forth in the aboveformula, and that a mixture of said solution with mineral oil willproduce a satisfactory core. is iscovery is important because of thefact that mineral oils are much less costly than vegetable oils whichare used in core manufacture, and the present invention thereforeprovides a market for inexpensive grades of mineral oil. While atcurrent market prices mineral oils are most costly by the gallon thanthe solution used in my invention, it is possible that the use ofmineral oils with the solution may reduce the total amount of liquidemployed in mixing with sand to produce a satisfactory core material, tothe extent that mineral oils used with my solution may be used at nogreater ultimate cost than if the solution were to be used alone.

I have referred to sand as one ingredient of my core, and it should beunderstood that the term sand" as used in the foregoing specificationand in the appended claims refers to any type of molding sand or othergranular material that is capable of being molded when moist.

The product made according to the method described above, like all coresand similar molded products, occasionally has a slight tendency toadhere to the core box or wooden mold in which it is formed. Thistendency, while considerably less in cores of the present invention thanin conventional cores, must be overcome whenever it is found to exist atall, and I have discovered that the addition of a small quantity ofglycerin or oil. say about one part of glycerin or oil to 500 parts ofthe above described solution, will satisfactorily prevent the adherenceof the core ma terial to the core box.

Burning ofthe core due to impinging of molten metal during the pouringoperation, which is ordinarily prevented by a coating of speciallypreprovision of an extremely hard, smooth external surface which ishighly resistant to the deleterious effect of molten metal being pouredagainst the core.

Many attempts have heretofore been made to use compounds of silicon as abinder for molded products, but have proven unsatisfactory because thebinder breaks down under the influence of either heat or moisture. Inthe present invention, however, even though sodium silicate is theprincipal ingredient of the binder, neither moisture nor heat willdestroy the molded product.

The invention is also adapted to the manufacture of the straightcylindrical cores, known as shop cores, by the extrusion process, andproduces a core that will not warp or bend, upon absorbing moisture,after it has been cured.

As is well known, there are generally two types of water-soluble sodiumsilicates namely, those in which the ratios 0 ago: 1 2 are 1:2 and 1:3respectively (Thorpe: isictionary of Applied Chemistry, Supplement, vol.2, 1935, page 377). The latter is more diflicultly soluble in water.However, aslong as it can be dissolved in water, it may be used, andother differences, for instance, in the content of water ofcrystallization as between sodium metasilicate and sodium pyrosilicate,are immaterial as far as my purpose is concerned.

Having thus described my invention, what I claim and desire to secure byLetters Patent is:

i. A baked molded product of sufficiently high tensile strength to beused as a core for metal casting purposes and having a high degree ofresistance to heat and moisture comprising a mixture of sand and abinder which comprises an aqueous solution of an alkali metal silicate,an alkali metal fluosilicate and a compound of boron.

2. A molded product of sufficient high tensile strength to be used as acore for metal casting purposes and having a high degree of resistanceto heat and moisture comprising a mixture of sand and a binder whichcomprises an aqueous solution of an alkali metal silicate, an alkalimetal fiuosilicate, aluminum sulfate and a compound of boron.

3. A baked molded product comprising sand and a binder which comprises amixture of a mineral oil, an aqueous soluble alkali metal silicate, andan alkali metal fiuosilicate.

4. A molded product of sufficient high tensile strength to be used as acore for metal casting purposes and having a high degree of resistanceto heat and moisture comprising a mixture of sand and a binder whichcomprises an aqueous solution of an alkali metal silicate, an alkalimetal fluosilicate, aluminum sulphate and a mineral oil.

5. In the manufacture of a baked product of sufliciently high tensilestrength to be used as a core for metal casting purposes the stepscomprising adding a binder consisting of an aqueous solution of analkali metal silicate, an alkali metal fluosilicate and a compound ofboron to sand and molding and baking the resulting mass.

6. In the manufacture of a baked product of sufficiently high tensilestrength to be used as a core for metal casting purposes the stepscomprising adding a binder consisting of a mineral oil, an aqueoussolution of a water-soluble alkali metal silicate and an alkali metalfluosilicate to sand and molding and baking the resulting mass.

ALLAN B. RUDDLE.

solution of a water-

